1. Field of the Invention
The present invention relates to a recording method, a recording apparatus, a reproducing method and a reproducing apparatus for use in recording or reproducing a disc that conforms to DVD (digital video disc or digital versatile disc) standards, for example.
2. Description of the Related Art
As media for recording contents data such as video data and audio data, media that conform to the DVD standards are now commercially available on the market. When classified from the standpoint of types of data recorded on the media, DVDs are generally classified into a DVD-video in which video data such as movies are recorded, a DVD-audio in which mainly audio data are recorded and the like.
Having classified the DVD standards from a standpoint of types of media, it is to be noted that, in addition to DVD-ROM which is the read-only type medium, there exist various kinds of media, such as DVD−R, DVD+R in which data can be recorded only once (i.e. data cannot be erased) and DVD−RW, DVD+RW, DVD-RAM in which data can be rewritten.
When contents data files are recorded on the DVD-video, the DVD-audio or the like, contents data may be encrypted and recorded on the media in view of preventing contents data recorded on the media from being used illegally. When contents data are encrypted to be recorded on a DVD standard disc, a method called a “CSS (content scrambling system)” is applied to the DVD-video, for example.
FIG. 1 is a schematic block diagram showing the CSS method applied to this DVD-video. In the case where this method is employed, a title key 2 that is an encryption key assigned to contents data file 1 such as video data and audio data is prepared. Further, there is prepared a disc key 3 that is an encryption key assigned to each disc. Then, there is provided a key issuing center 4that manages encryption. The key issuing center 4 encrypts the disc key 3 using a master key managed by the issuing center 4 and further encrypts the title key 2 using the disc key 3.
Then, after a data compression processing unit 5 has compressed contents data 1 in accordance with MPEG (Moving Picture Coding Experts Group) encode processing, a scramble processing unit 6 scrambles contents data 1 using the title key 2 encrypted by the key issuing center 4. The encrypted contents data 1, and the disc key 3 and title key 2 encrypted at the key issuing center 4 are recorded on a disc at a disc manufacturing process 7. The disc key 3 is recorded on a lead-in area of the disc and the title key 2 is recorded on each sector of contents data having a sector structure.
Specifically, FIG. 2 shows an arrangement of a lead-in area, in the DVD, that should be first read out by the reproducing apparatus when the disc is reproduced. As shown in FIG. 2, the lead-in area uses sectors from the physical sector number is 0 h (reference letter h represents the hexadecimal notation: this representation applies to the following description as well) to the sector located just before 30000 h. A first area in which all values are null is followed by a sector in which a reference code is located, which is again followed by an area in which all values are null. Then, there is provided a control data area. Thereafter, there is further provided an area in which all values are null and then, from the sector number 30000 h a main data area in which contents data are recorded is provided.
In the control data area, physical format information is located at the first one sector (sector 0), disc manufacturing information is located at the next one sector (sector 1) and contents provider information is located-at the next 14 sectors (sectors 2 to 15). Information of these 16 sectors from the sector 0 to the sector 15 is repeatedly located in the control data area. Then, a disc key unique to the disc is located in the area in which contents provider information is located.
Then, a structure in which title key is recorded is described with reference to an example of a sector structure in FIG. 3. Each sector on which main data such as contents data are recorded is composed of 2064 bytes. Headmost four bytes of the 2064 bytes are assigned to ID data indicating the sector number and the like, and the succeeding two bytes are assigned to error-detection data for ID data. Further, the next six bytes are assigned to copyright management information (copy management data), and a title key is provided in this copyright management information. Then, 2048 bytes following the copyright management information are assigned to the main data recording area in which contents data and the like are recorded. Further, the last four bytes are assigned to error-detection data for the whole of this sector.
Fundamentally, data in a read-only disc are thus encrypted and stored using the disc key and title key. However, there are discs of DVD standards in which data can be recorded. For example, the DVD−R/RW standard disc is able to record data. Therefore, if processing so-called a bit by bit copy in which digital data reproduced from other medium is directly recorded on another medium is performed, the data read out from the DVD-video is directly recorded on the DVD−R/RW standard disc, whereby the disc of the DVD-video may be copied illegally. However, when the above-mentioned disc key and title key are prepared, contents data such as video data recorded on the illegally-copied disc cannot be decoded from encryption.
With reference to FIG. 4, there will be described the reason that contents data such as video data on the illegally-copied disc cannot be decoded from encryption. First, there is prepared a disc Da of read-only DVD-video in which the disc key and the title key are provided and recorded as described above, and this disc Da is reproduced by a user so that in a reproducing apparatus the disc key is obtained at the lead-in area of the innermost periphery of the disc and the title key is obtained from the sector in which the contents data had been recorded. Then, contents data can be correctly decoded from encryption by using the disc key and the title key obtained from this reproduction and there can be obtained decoded video data and audio data.
Assume that a user executes a bit by bit copy and records the contents data recorded on the disc Da of this DVD-video on a disc Db of a DVD−R/RW standard. In the disc Db of the DVD−R/RW standard, a part of the lead-in area is designated as an area in which data have already been recorded by pits when a disc is manufactured, and a disc key allocated to the disc Db or a dummy key has been recorded in the already-written area in advance.
Accordingly, when a user manufactures a disc Db′ in which contents data read out from the disc Da of the DVD-video is directly recorded without modifying the sector structure, the copied disc Db′ of the DVD−R/RW standard has a disc key including different key data compared with the original disc Da. Since the disc key is different from that of the original disc Da, even when the user intends to reproduce the copied disc Db′, the reproducing apparatus is unable to correctly decode the disc key different from that applied in the manufacturing of the original disk. As a result, illegal use of the copied disc can be prevented.
Although the case where the CSS method is mainly applied to a DVD-video disc has so far been described, the fundamental principle is the same in the case where a CPPM (Content Protection for Pre-recorded) that is the scramble system applied to the disc of the DVD-audio is considered.
Now, if dummy data are recorded in advance, that is when a disc is manufactured, in the control data area of the data recordable disc in order that the disc is prevented from being written a disc key, there arises a problem of taking plenty of time and much labor to manufacture discs. Consequently, costs of manufacturing discs (media) will increase. Further, if data are recorded in advance on the lead-in area of the recordable disc, data area management information cannot be written and cannot be used for a test of writing or the like. Thus, there arises a problem that a recording area prepared for the medium cannot be utilized effectively.
From these standpoints, recording in the lead-in area also should preferably be performed by a recording apparatus when data are recorded. In future recordable discs, it is expected that their lead-in areas also can be recorded by the recording apparatus side. In the case of the medium in which data can be recorded on the whole surface of the disc, data such as DVD-video can be directly copied including those in the lead-in area. However, such arrangement is not preferable in view of protecting copyright of contents data, and hence some countermeasure should be required.
While the problems in the illegal copy control processing in the case of the DVD standard has been described so far, similar problems will arise in illegal copy control processing in media of other standards. Similar problems will also arise when media other than discs are used as recording media.